N-(phosphonomethyl)glycine is a broad spectrum systemic non-selective herbicide generically known as Glyphosate. It is effective for control of annual and perennial plants including grasses, sedges, broad-leaved weeds and woody plants.
Glyphosate is commonly used in salt form such as isopropylamine salt, trimethylsulfonium salt, ammonium salt etc. However, the difference in efficacy of various brands is more likely to be due to the adjuvants used in the formulation and tank-mix rather than the type of salt itself. Many adjuvants are available to improve spreading, deposition and rain-fastness of glyphosate formulation.
The effectiveness of a formulation as well as its suitability from environmental point of view, both are important. Among the available adjuvants, those which are safe to the environment are preferable.
Ammonium sulfate is added to glyphosate formulations in order to improve its performance under stressful conditions, especially when hard water is used to prepare spray solution.
Various types of formulations of Glyphosate are commercially available such as suspension concentrate, water soluble or dispersible granules etc. The granular form is more popular and preferred over other forms.
Numerous compositions and processes have been disclosed in the literature for preparation of granular formulation of ammonium glyphosate using various adjuvants. These include patents/applications viz. WO9007275, EP252897, WO2007112933, WO2006133788, JP2005112836, US2004102323, U.S. Pat. No. 5,858,921, WO9800022, EP0378985 and EP0582561. Tallow amine surfactants are most commonly used in these glyphosate formulations. European patent EP0378985 discloses a granular formulation of glyphosate salt in which the most preferred surfactant is an ethoxylated tallow amine containing 15-18 moles of ethylene oxide. WO2006133788 describes a process for preparing water-soluble ammonic glyphosate granules in which tallow amine surfactant is preferably used.
Though glyphosate itself is practically non-toxic to fish, the toxicity is due to tallow amine surfactant used in the formulation. Therefore such formulations are not suitable for use in or close to aquatic environment. Tallow amine surfactants are also irritants to eyes & skin. Therefore it is preferable to have a glyphosate formulation in which non-tallow amine surfactants are used.
U.S. Pat. No. 6,248,695 discloses herbicidal composition comprising glyphosate or its salt and an alkyldiamine tetraalkoxylate surfactant. It also claims the use of alkyl glycoside or alkyl polyglycoside surfactants along with alkyldiamine tetraalkoxylate in glyphosate or its salt containing composition. However, in the said patent, the surfactant requirement is as high as 21-22 wt %. In the formulation described in said patent, alkyl glycoside or alkyl polyglycoside is not used without using alkyldiamine tetraalkoxylate simultaneously. Moreover, in the said patent, the formulation of isopropylamine salt of glyphosate is in liquid form when alkyl glycoside is used.
The use of alkyl glycoside or alkyl polyglycoside surfactants in granular formulation of ammonium salt of glyphosate is not known in the art.